This is ongoing research and development. The capability to calculate the distribution of absorbed dose produced by photon beams and electron beams of the most general characteristics is fundamental to radiotherapy. The radiation field model has been described before. It takes as a basis the empirical distributions along three mutually perpendicular reference lines in a "master field." This concept is applied to the beam-modifying devices as well. One virtue of this approach is that it requires few experimental data and thus can be implemented very easily. A completely new approach to electron field modeling has been developed and published in 1987. Its application to unit density media has been implemented. Extension to inhomogeneous media is underway. Of special interest are the implications for easy handling of different electron energies and field shapes in combination with photon fields.